What is a static ip address?
Each owner of a computer which is connected to the web through an ISP [Internet Service provider] is allocated a web address of the form a.b.c.d where a, b, c and d are integer numbers between 0 and 255.
An example of a web address is 126.96.36.199
Now then, a static web address is one that is manually assigned to your computer by a network or computer administrator. The result of this manual assignment is that your IP address always stays the same until/unless you manually change it to something else yourself. To be able to manually assign a static IP to your computer that can be used on the internet you must first ask your ISP to allocate a static IP for you to use. They will then tell you what IP they have set aside for you to use, and you may then manually input that IP into your computer.
On the other hand, a dynamic address means that the address that is automatically assigned to your computer by your ISP each time you log onto the internet. IPs that are allocated dynamically are usually different every time you log on to the internet.
A common misconception is that a static IP is the same thing as an IP that doesn't change. While it is true that a static IP does not change, it is not always true that an IP that doesn't change is a static IP, as this is not the defining characteristic of a static IP. An IP that does not change but is still automatically assigned by your ISP is sometimes referred to as a "sticky IP" to distinguish it from a true static IP. By definition, if you do not manually enter the IP address directly into your computer, it is not a static IP address - even if the address that is automatically assigned to you never changes. There are two reason why the distinction between static IP and "sticky IP" is critical:
1) Static IPs can have their authority delegated to a DNS server of your choosing for reverse DNS resolution. "Sticky IPs" cannot do this, and reverse DNS resolution will always resolve to the ISP that is assigning them. This is important for many business-class services, such as email, where the correct reverse DNS resolution is necessary for the service to work properly.
2) When you have more than one "sticky IP" from your ISP you cannot guarantee which computer will be automatically assigned to which "sticky IP". This is opposed to true static IPs, because by definition you enter a static IP directly into the computer, so you can guarantee which computer always uses which IP. To illustrate this point, consider computers A and B, and IP addresses 188.8.131.52 and 184.108.40.206:
Computer A is statically assigned IP 220.127.116.11, and computer B is statically assigned IP 18.104.22.168. The power goes out, and then comes back on. When both computer A and computer B are finished booting, they each have the same IP address as they did before the power went out because their IP addresses were set directly into the computers themselves.
Now consider a "sticky IP" situation. Computer A logs into their ISP and the ISP assigns computer A the IP 22.214.171.124. Computer B logs in after computer A and the ISP assigns computer B the IP 126.96.36.199. The power goes out, only this time computer B is the first to boot up and connect to the internet. The ISP may now assign IP 188.8.131.52 to computer B as it is the first computer to reconnect. Anybody on the internet that is expecting to reach computer A with the IP 184.108.40.206 will now be communicating with the wrong computer.
Computers that connect to the Internet are given a unique address called an Internet Protocol (IP) address. A static IP address is permanently associated with a computer and cannot be changed.